Background: Presenting smokers with evidence of early lung damage is believed to increase quit rates; however, a Cochrane review found insufficient evidence to support the use of personal biomarkers in smoking cessation strategies. Parkes and colleagues studied the impact of informing smokers of their "lung age" (age of the average person who has a forced expiratory volume [FEV₁] equal to the smoker) on quit rates.

The Study: Smokers 35 years and older were recruited from five general practices in one county in England. Patients using oxygen and those with a history of tuberculosis, lung cancer, asbestosis, silicosis, bronchiectasis, or pneumonectomy were not eligible for the study. The baseline assessment included medical and smoking history, medication use, and standardized assessments of the impact of respiratory disease on daily life (the St. George's respiratory questionnaire) and of the smoker's readiness to change. Spirometry was completed on all participants to assess FEV₁, forced vital capacity (FVC), and the FEV₁/FVC ratio. The FEV₁ results were used to estimate a lung age for each smoker.

More than 500 participants were randomly allocated to the intervention or control group. All participants were encouraged to quit smoking and were provided information on locally available smoking cessation services. Participants in the intervention group were also provided with verbal and illustrative information about their lung age and were counseled that quitting would slow the rate of deterioration in lung function. Persons in the control group only received numerical spirometry results. Spirometry was offered again after 12 months. The primary outcome was confirmed smoking cessation at 12 months. Self-reported quitting was confirmed by carbon monoxide breath testing and cotinine saliva levels. Secondary outcomes included daily cigarette use and new diagnoses of medical conditions.

Results: The control group (281 participants) included significantly more persons with a history of stroke than the intervention group (280 participants), but the groups did not differ significantly in any other variable. The average participant reported 33 pack-years of smoking, and 20 percent had significant comorbidities. Abnormal lung function was found in 23.5 percent of persons in the control group and 26.8 percent of persons in the intervention group.

Thirty-two persons from the control group and 31 from the intervention group did not return for follow-up. Assuming these participants continued to smoke, the verified quit rates were 6.4 percent in the control group and 13.6 percent in the intervention group. This difference is highly statistically significant. The estimated number needed to treat for the intervention to achieve one additional quitter was 14. In those who continued to smoke, the average daily cigarette use was significantly lower in the intervention group (11.7 compared with 13.7). The estimated cost of the intervention was $40 per patient processed or $556 per successful quitter.

Conclusion: The authors conclude that informing smokers of their lung age is associated with comparable quit rates to other strategies, such as counseling, nicotine replacement, or pharmacologic aids. The severity of lung damage on spirometry did not appear to be associated with the chances of quitting, but the study did not have sufficient power to establish any significant association.